The present disclosure relates generally to Digital to Analog Converters (DACs). Specifically, the present disclosure relates to systems and methods that provide both active charge-sharing and passive charge-sharing in a conversion operation.
Most Liquid Crystal Display (LCD) panels include an array of pixels that are driven by signals on rows and columns to address the individual pixels. An example column driver includes a multitude of DACs that receive video signals as digital bits and output analog signals that can be applied to the pixels to render a desired image.
An example DAC uses a passive charge-sharing technique during conversion. Passive charge-sharing conversion can provide desirable speed for some applications. However, parasitic capacitance arises in switch circuitry in passive charge-sharing devices and may lead to non-linear performance. As a result, some applications include a large-sized capacitor array, which helps with linearity but takes up more space on a semiconductor die.
Another example DAC uses an active charge-sharing technique during conversion. The active charge-sharing technique uses negative feedback at an op-amp to ensure linear operation. However, the op-amp settling time can be tight. Thus, in order to meet DAC convention timing specifications, high power consumption is used in the op-amp.
Therefore, designers of DACs in some applications have to choose between adding space on the die to accommodate passive charge-sharing or consuming large amounts of energy for active charge sharing. More efficient and effective DACs are called for.